1. Field of the Invention
The present invention relates to an audio system reproducing sound energy to cause bodily sensation, and more particularly to an on-vehicle audio system reproducing bodily sensible sounds.
2. Description of Background Information
Audio systems reproducing bodily-sensible sounds are devised to convert low frequency band component signals extracted from audio signals to mechanical vibrations to have a listener directly and bodily sense the vibrations, in addition to producing acoustic effects by an acoustic transducer such as a speaker which transmits music sounds through air propagation, thereby reproducing realistic sounds.
FIG. 1 illustrates the configuration of a conventional on-vehicle audio system reproducing bodily-sensible sounds.
A volume adjusting means 1 allows a listener to manually adjust a volume of an inputted music sound signal, and supplies a compressor 2 and an amplifier 3 with the adjusted music sound signal. The music sound signal then is amplified by the amplifier 3 and reproduced by a speaker 4. The speaker 4 is placed at an appropriate position in a vehicle cabin. The compressor 2 adds to the music sound signal a gain as indicated by a solid line in FIG. 2 to compress the level thereof, and supplies a low pass filter 5 with the compressed music sound signal. The level of the music sound signal is maintained by the compressor 2 at a level at which a human can feel pleasant low sounds. The low pass filter 5 only supplies low frequency band components to an amplifier 6. It is considered that the appropriate cut-off frequency of the low pass filter 5 is, for example, approximately 120 Hz, -12 dB/oct. The amplifier 6 amplifies the low frequency band component signal and supplies the amplified signal to a bodily-sensible sounds generation unit 8 built in a seat 7.
In the on-vehicle audio system reproducing bodily-sensible sounds, the passenger manipulates the volume adjusting means 1 to obtain reproduced sounds and bodily-sensible sounds at an arbitrary magnitude.
However, in a vehicle cabin susceptible to the influence of vibrations from the outside, since vibrations due to the running vehicle mask bodily-acoustic low sounds, a problem arises that the original bodily acoustic vibrations cannot be obtained. As a method of eliminating such masking, the level of the audio system reproducing bodily-sensible sounds is adjusted in accordance with such vibrations of the running vehicle, wherein the level of the audio system reproducing bodily-sensible sounds has been adjusted by a manual volume adjusting means. However, it is impossible to manually adjust the level in a timely manner, thus presenting a problem that a listener will have an inharmonious feeling when "listening" the bodily-sensible sounds.